The present invention relates generally to a data processing apparatus for facilitating data error concealment.
Recently, recording media significantly enhanced in recording rate, such as optical disks and so on, are in practical use, realizing the long-time recording of video data with comparatively high picture quality.
However, as compared with audio data and text data, video data are huge in data volume, so that the processing of video data requires significantly much heavier load than that in the processing of audio data and text data, despite of the rapid enhancement in the recording rate of recording media.
In order to reduce the recording rate while restricting picture quality deterioration, a method is known in which video data is compressed by means of MPEG (Moving Picture Experts Group) encoding for example.
However, if video data is compressed by the MPEG encoding for example, the decoding of compressed video data sometimes takes much time.
To be more specific, in MPEG, a long GOP is sometimes employed as a GOP (Group Of Pictures). With a long GOP, the reproduction of a frame (or a field) sometimes requires to reproduce another long-GOP frame.
Because MPEG is required to decode another frame in order to decode a certain frame as described above, it is difficult to cope with errors, if any, in the data read from an optical disk, namely it is difficult to execute error concealment.
To be more specific, if a long GOP is employed, one GOP is formed by 15 frames, in order to decode a P-picture and a B picture in the frames forming this one GOP, an I-picture or a P-picture that is another frame must sometimes be required. Therefore, if an error occurs in an I-picture frame forming a long GOP, failing the decoding thereof, all frames forming this long GOP, namely 15 frames, may not be decoded. As a result, let the frame period be 1/30 second, then the video data cannot be outputted for as long as 0.5 (=15× 1/30) second.
Further, with a long GOP, the decoding of the B picture of a GOP may require the P-picture of a GOP one step before that GOP. Therefore, if the I-picture forming a GOP cannot be decoded due to an error, all frames of that GOP and some of the frames of the next GOP may not be decoded.
For this reason, when video data is encoded by MPEG and recorded to an optical disk, counter error measures such as enhancing error correction capabilities may be taken; however, it is still difficult for this approach to perform high redundant, complete error correction.
For the encoding within a frame other than a long GOP frame, error correction may be sometimes impossible.
To solve this problem, a method is proposed in which same video data is recorded in separate recording areas of an optical disk before hand and, if an error occurs on the video data recorded in one recording area, the failing error portion is replaced with the video data recorded in another recording area.
However, if an error occurs on the video data recorded in a particular recording area and the video data recorded in another recording area are read in replacement, a seek time, a rotational delay time, and a time for reading the video data are required, thereby making it difficult to reproduce the video data real-time.
Also, a method is proposed in which, if, in recording video data on an optical disk, an error occurs at a position on the optical disk due to the recording of pixels or blocks in a spatial or temporal proximity with each other to discontinuous positions on the optical disk, the video data in a frame is protected from total destruction by the error and the failing video data portion is interpolated with the error-free corresponding video data.
However, in this method, if an error occurs, a circuit dedicated to video data interpolation, namely a circuit dedicated to error concealment, is required, thereby enlarging equipment scale. In addition, this method involves the degradation in compression efficiency because pixels and blocks in a spatial or temporal proximity with each other are recorded to discontinuous positions on an optical disk.